Caption: Pan across dead trees killed by rising water levels at the southern end of Yellowstone Lake, in Yellowstone National Park, Wyoming, USA. The water levels have risen due to the growth of an enormous magma chamber that underlies much of the park. Liquid magma at high pressure has inflated the ground beneath the northern part of the lake, raising it and tipping the southern end downwards, leading to the shift in water levels. The Yellowstone magma chamber has been responsible for at least three huge volcanic eruptions in the last 2.1 million years, with the last some 640,000 years ago. Such an eruption today would be catastrophic for the region and would have a long-lasting global effect on the human population. The Yellowstone Supervolcano, as it is known, is under constant surveillance.